Welded seams by type of connection. Welding seams. Main types of welding joints

Welds - zones of welded joints, which are formed by initially molten metal, and then crystallized upon cooling.

The service life of the entire welding structure depends on the quality of the welds. The quality of welding is characterized by the following geometric parameters of the weld:

• Width - the distance between its edges;
• The root is the inner part opposite to its outer surface;
• Convexity - the largest protrusion from the surface of the metal being joined;
• Concavity - the greatest deflection from the surface of the metal being joined;
• A leg is one of the equal sides of a triangle inscribed in the cross section of two connected elements.

What are the welds and joints, classification

Table 1 shows the main types of welding joints, grouped by cross-sectional shape.

	Welded joints and seams	Location features	Main application	Note
1	Butt	The parts to be connected, the elements are in the same plane.	Welding of sheet metal structures, tanks and pipelines.	Saving consumables and time for welding, connection strength. Careful metal preparation and selection of electrodes.
2	corner	The parts to be connected, the elements are located at any angle relative to each other.	Welding of containers, reservoirs.	The maximum metal thickness is 3 mm.
3	Lap	Parallel arrangement of parts.	Welding of sheet metal structures up to 12 mm.	Large consumption of material without careful processing.
4	T-shaped (letter T)	The end of one element and the side of the other are at an angle	Welding of load-bearing structures.	Careful processing of the vertical sheet.
5	End	The side surfaces of the parts are adjacent to each other	Welding of vessels without pressure	Material savings and ease of execution

By way of execution:

• Double-sided - welding from two opposite sides with the removal of the root of the first side;
• Single-layer - execution in one "pass", with one deposited bead;
• Multilayer - the number of layers is equal to the number of "passes". It is applied at a big thickness of metal.

According to the degree of convexity:

• Convex - reinforced;
• Concave - weakened;
• Normal are flat.

The convexity of the seam is affected by the welding materials used, the modes and speed of welding, the width of the groove.

By position in space:

• Lower - welding is carried out at an angle of 0 ° - the most optimal option, high productivity and quality;
• Horizontal - welding is carried out at an angle from 0 to 60 ° require increased
• Vertical - welding is carried out at an angle from 60 to 120 ° qualification of the welder;
• Ceiling - welding is carried out at an angle of 120 to 180 ° - the most time-consuming, unsafe, welders undergo special training.

By length:

• Solid - the most common;
• Intermittent - leakage of the structure.

Types of welded joints and seams by relative position:

• Arranged in a straight line;
• Arranged in a curved line;
• Arranged in a circle.

In the direction of the acting force and the vector of action of external forces:

• flank - along the axis of the welded joint;
• frontal - across the axis of the welded joint;
• combined - a combination of flank and frontal;
• oblique - at a certain angle to the axis of the welded joint.

Types of welds according to the shape of the products to be welded:

• on flat surfaces;
• on spherical ones.

The types of seams also depend on the thickness of the working material and on the length of the joint itself:

• short - not > 25 cm, while welding is carried out using the “in one pass” method;
• medium - long< 100 см – используется обратно-ступенчатый способ сварки, при этом строчка разбивается на малые отрезки длиной в 100-300 мм;

All long seams are processed in a reverse-step way, from the center to the edges.

Cutting edges for welding

To create a strong and high-quality weld, the edges of the products to be joined undergo the necessary preparation and they are given a certain shape (V, X, U, I, K, J, Y - figurative). To avoid burn-through, edge preparation can be performed with a metal thickness of at least 3 mm.

Edge preparation procedure:

1. Cleaning the edges of the metal from rust and dirt;
2. Chamfering of a certain size - depending on the welding method;
3. The gap size depends on the type of welded joints.

Edge preparation options:

Table 2 shows the features of edge preparation depending on the thickness of the metal.

table 2

Welds and joints are classified according to various criteria. It is also important to understand that these are different concepts.

A weld is that place in the metal that is in a molten state during welding. And when the metal cools, the seam crystallizes. A welded joint is a broader concept. The connection directly includes the seam itself, as well as adjacent zones, namely: the zone that was subjected to thermal stress during the welding process, the fusion zone, the part of the metal that is located near the zone subjected to heating.

It is important to distinguish between welds and joints, since the properties of the former determine the shape and strength of the metal in the place where welding took place. And the properties of the joint are determined by the properties of the seam itself and other zones of the joint, plastic deformations and, accordingly, affect the nature of the distribution of forces that will act in the welded joint.

It is also worth understanding that in one welded joint there can be from one or more seams.

In order to understand in what situations and for what work certain welding seams and joints are used, one should familiarize oneself with their characteristics in detail.

Types of welds and their characteristics.

The classification of welds occurs according to the following criteria:

Cross section shape:

• Butt - elements located in the same plane are butted and welded.
• Corner - elements are welded at a certain angle.
• Slotted - elements (sheets) are superimposed on each other and melted into each other.

The main difference is the different geometry and basic parameters of the seams. If, for example, at the butt weld, the height of reinforcement and width are the main ones, then in the corner - the leg of the seam.

Weld configuration:

• Rectilinear.
• Curvilinear.
• Ring.

Weld length:

• Solid ones are divided into short ones - their length is no more than 300 mm, medium ones - up to 1 meter and long ones - more than 1 meter.
• Intermittent - they can have a chain and staggered arrangement of seams on a welded joint.

Welding method used:

• Made by consumable electrode by manual arc welding.
• Made in a gaseous environment with a consumable electrode.

Number of seam layers:

• Unilateral.
• Bilateral.
• Multilayer.

Deposited metal volume:

• Normal.
• Reinforced.
• Weakened.

Welding joints: types and properties.

The main feature by which welded joints are classified is the arrangement of elements relative to each other. Based on this, the following types are distinguished:

• Butt - their formation is determined by the creation of butt-type seams.
• Fillet - are created when welding fillet welds.
• Lap - these connections are also formed with the help of corner, as well as with the help of slotted seams.
• T-shaped - fillet welds are also used to create such joints, less often slotted ones.

Butt joints the most common, as they have the lowest stress value, and are also the least susceptible to deformation during the welding process. This type of joints is the least consumable for metal, but also requires the most thorough preparation of parts before direct welding. With the help of butt welds, metal products with a thickness of 1 to 60 mm can be welded. For each thickness, there are recommendations on the shape of the bevel of the edges of the sheet - X-shaped, Y-shaped U-shaped and so on.

Corner connections- welding elements are located at any angle to one another, but do not carry much stress. Various vessels, containers, reservoirs - most often welded in this way. The thickness of the metal does not exceed 1-3 mm.

Lap connections- this type of joint does not require special processing of the edges of the metal, as in butt welding, but the consumption of metal - the main and deposited will be large. The thickness of the metal for this type of welding is no more than 12 mm. Most often, a double-sided seam is used so that moisture does not penetrate from the opposite side of the seam.

Tee connections - truss frames, columns, posts, beams are most often welded using this type of connection. In cross section, this connection is the letter T, and the weld can be on one or both sides.

Before starting any welding work, it is important to get an idea of ​​what types of welds and joints exist. This information will help you efficiently use resources when performing work and will give an idea for which products it is preferable to use certain welds and connections.

The main types of welded joints are butt, corner, tee and overlap:

- butt (C)- the parts are joined end-to-end along the end surfaces (Fig. 1a);

- angular (U) - the parts are located at an angle and are connected along the edges outside the corner (Fig. 1b);

- tee (T)- the details form the shape of the letter T (Fig. 1c);

- overlap (N)– parts partially overlap each other (Fig. 1d).

The seams of these joints are designated by a letter with an index corresponding to the specific nature of the seam (Table 3). Seams of welded joints are performed without bevel edges, with a bevel of one edge, with a bevel of two edges and in butt joints with flanging of two edges.

a B C D)

Picture 1 - The main types of welded joints:

a) butt; b) angular; c) tee; d) overlap

3 Symbols and designations of welds

For each welding method, standards have been developed that indicate the structural elements of the seams, their conditional images and designations.

By the nature of the execution, the seams can be point, intermittent, continuous, i.e. continuous. An intermittent seam is performed either in a chain or in a checkerboard pattern.

Solid visible seams of welded joints are depicted by a solid main line (Fig. 2a); and invisible ones are dashed (Fig. 2b). In this case, the side from which welding is performed is taken as the front side of the one-sided seam of the welded joint. For the front side of the double-sided seam of a welded joint with asymmetrically prepared edges, the one from which the main seam is welded is taken. Any side can be taken as the front side of a double-sided seam with symmetrically prepared edges.

Figure 2 - Conditional images of seams:

a) visible; b) invisible

Visible single welded spots, regardless of the welding method, are conventionally depicted by intersecting thin solid lines 5 ... 10 mm long (Fig. 2a). Invisible single points are not depicted in the drawings.

If there are several identical seams in the drawing, symbols are applied to one image, and leader lines with shelves are drawn from the rest (Fig. 3a, b).

Identical seams are assigned one number, which is applied on the leader line with a shelf on which the seam designation is located, and the number of seams is indicated (Fig. 3a).

For the rest of the seams, only the number of the seam is applied, respectively, above the flange or under the flange of the leader line, depending on the visibility of the weld (Fig. 3b).

Figure 3 - Conditional images if there are identical seams in the drawing:

a) one image; b) for identical images; c) simplified or all seams in the drawing are the same.

If all the seams in the drawing are the same and are shown on the same side (front or back), they are not assigned a serial number, and the seams without designation are marked with leader lines, without shelves (Fig. 3c).

A leader line for designating a weld is applied from the welding side and preferably on the image of the part where the weld is drawn in actual size.

In the drawing of a symmetrical product, it is allowed to mark the seams on only one part of the image.

The symbol for the seam is applied:

On the shelf of the leader line drawn from the image of the seam on the front side (Fig. 3a);

Under the shelf of the leader line drawn from the image of the seam on the reverse side (Fig. 3b). In this case, it is preferable to draw a leader line from the image of a visible seam.

The leader line drawn from the image of a seam or a single weld point always ends with a one-way arrow (Fig. 3). If the weld is invisible, then a one-sided arrow is drawn on top of the leader line, if the weld is invisible, from below (Fig. 3a, b).

The same requirements for all seams or a group of seams are given once in the technical requirements or in the table of seams (Fig. 4). In this case, only the serial number of the weld is indicated on the image.

Picture 4 - Table of seams

The symbol for standard welded joints in accordance with GOST 2.312-72 is applied according to the scheme, in accordance with Figure 5.

Figure 5 - Scheme of the symbol for standard welds.

The symbolic designation of the seams of welded joints through the signs "hyphen" includes:

1. Auxiliary signs of a seam along a closed line and an assembly seam (see table. 2).

2. Designation of the standard for types and structural elements of welded joints (for example, GOST 5264-80; see table. 1).

3. Alphanumeric designation of the seam according to the standard for the types and structural elements of the seams of welded joints (for example, C2, see Table 3).

4. Symbol for the welding method according to the standard for the types and structural elements of the welds of welded joints (for example, A, but you can not specify).

Table 2 - Auxiliary signs for the designation of seam welding

5. The sign of the leg of the weld  (isosceles right-angled triangle) and the size of the leg (thickness) of the weld, according to the standard, for the types and structural elements of the welds of welded joints (for example, 5, Table 3). The thickness of the seam should be in the range from 4 mm to 1.2 of the thickness of the connected elements or equal. The sign is made with solid thin lines. The height of the sign must be the same as the height of the numbers included in the designation of the seam.

6. For an intermittent seam - the size of the length of the welded area, the sign / or Z and the step size (for example, 5/40; 6 Z 70).

For a single spot weld - the size of the calculated spot diameter (for example, 6).

For a contact spot electric welding or electric rivet weld - the size of the estimated diameter of the point or electric rivet; sign / or Z and step size (for example, 5/60; 4 Z 80).

For a contact roller electric welding seam - the size of the calculated width of the seam (for example, Kr-5).

For an intermittent weld of contact roller electric welding - the size of the calculated width of the seam, the multiplication sign "", the size of the length of the welded area, the sign / and the step size (for example, 5  10/60).

Table 3 - Alphanumeric designation of the seam according to the standard for the types and structural elements of the seams of welded joints

7. Other auxiliary signs (see Table 2).

8. The roughness of the mechanical processing of the surface of the seam (for educational purposes, you can not specify).

Terms and definitions for welded structures, assemblies, joints and seams are established by GOST 2601-84.

A welded joint is a permanent connection of two or more elements (parts) made by welding. A welded joint includes a weld, an adjacent area of ​​the base metal with structural and other changes as a result of the thermal action of welding (the heat-affected zone) and areas of the base metal adjacent to it.

A weld is a section of a welded joint formed as a result of crystallization of molten metal or as a result of plastic deformation during pressure welding or a combination of crystallization and deformation.

A welded assembly is a part of a welded structure in which elements adjacent to each other are welded.

A welded structure is a metal structure made from individual parts or assemblies by welding.

The metal of the parts to be joined by welding is called the base metal.

The metal supplied to the arc zone in addition to the molten base metal is called filler metal.

The remelted filler metal introduced into the weld pool or welded onto the base metal is called weld metal.

The alloy formed by the remelted base or base and deposited metals is called the weld metal.

The performance of a welded product is determined by the type of welded joint, the shape and dimensions of welded joints and seams, their location relative to the acting forces, the smoothness of the transition from the weld to the base metal, etc.

When choosing the type of welded joint, the operating conditions (static or dynamic loads), the method and conditions for manufacturing the welded structure (manual welding, automatic welding in factory or installation conditions), savings in the base metal, electrodes, etc. are taken into account.

Types of welded joints. According to the form of conjugation of the parts (elements) to be joined, the following types of welded joints are distinguished: butt, corner, tee, lap (Figure 1).

Picture 1 -

Welds are divided according to the cross-sectional shape into butt (Figure 2.a) and fillet (Figure 2.b). A variation of these types are cork seams (Figure 2.c) and slotted seams (Figure 2.d), performed in overlap joints. According to the shape in the longitudinal direction, continuous and intermittent seams are distinguished.

With the help of butt welds, mainly butt joints are formed (Figure 1.a), with the help of fillet welds - tee, cross, corner and lap joints (Figure 1.b - 1.d), with the help of cork and slotted joints, lap joints can be formed and sometimes tee joints.

Butt welds, as a rule, are continuous; a distinctive feature for them is usually the shape of the cutting edges of the parts to be joined in cross section. On this basis, the following main types of butt welds are distinguished: with flanging edges (Figure 3.a); without cutting edges - one-sided and two-sided (Figure 3.b); with cutting one edge - one-sided, two-sided; with a rectilinear or curvilinear form of cutting (Figure 3.c); with one-sided cutting of two edges; with V-shaped cutting (Figure 3.d); with bilateral cutting of two edges; X-shaped cutting (Figure 3.e). The groove can be formed by straight lines (beveled edges) or have a curved shape (U-shaped groove, figure 3.e).

Figure 2 -

The butt joint is most common in welded structures, since it has a number of advantages over other types of joints. It is used in a wide range of thicknesses of welded parts from tenths of a millimeter to hundreds of millimeters in almost all welding methods. With a butt joint, less filler material is consumed for the formation of a seam, it is easy and convenient to control the quality.

Fillet welds are distinguished by the shape of the preparation of the edges to be welded in cross section and the continuity of the weld along the length.

According to the cross-sectional shape, fillet welds can be without edge cutting (Figure 4.a), with one-sided edge cutting (Figure 4.b), with two-sided edge cutting (Figure 4.c). In terms of length, fillet welds can be continuous (Figure 5. a) and intermittent (Figure 5.b), with a staggered (Figure 5.c) and chain (Figure 5.d) arrangement of the seam segments. T-joints, lap joints and corner joints can be made with segments of seams of small length - spot seams (Figure 5.e).

Figure 4 -

Figure 4 - Preparation of edges of fillet welds of tee joints: a - without cutting edges; b, c - with cutting edge

Cork seams in terms of their shape in plan (top view) usually have a round shape and are obtained as a result of complete penetration of the upper and partial penetration of the lower sheets (Figure 6.a) - they are often called electric rivets - or by melting the top sheet through the previously made in the top sheet hole (Figure 6.b).

Figure 5 -

Figure 6 -

Slotted seams, usually of an elongated shape, are obtained by welding the upper (covering) sheet to the lower fillet weld along the perimeter of the slot (Figure 6. c). In some cases, the slot can be filled completely.

The shape of the edge preparation and their assembly for welding are characterized by four main structural elements (Figure 7): gap b, bluntness c, bevel angle of the edge in and edge preparation angle a, equal to b or 2b.

Existing methods of arc welding without cutting edges allow welding metal of limited thickness (with one-sided manual welding - up to 4 mm, mechanized submerged arc welding - up to 18 mm). Therefore, when welding thick metal, it is necessary to cut the edges. The bevel angle of the edge provides a certain value of the angle of cutting the edges, which is necessary for the access of the arc deep into the joint and complete penetration of the edges through their entire thickness.

Figure 7 -

The standard angle of cutting edges, depending on the method of welding and the type of connection, varies from (60 ± 5) to (20 ± 5) degrees. The type of groove and the value of the groove angle determine the amount of additional metal required to fill the groove, and hence the welding productivity. So, for example, X-shaped cutting of edges in comparison with V-shaped allows to reduce the volume of deposited metal by 1.6 - 1.7 times. Reduced edge processing time. True, in this case, it becomes necessary to weld on one side of the seam in an uncomfortable overhead position or turn over the products to be welded.

Dullness c is usually (2 ± 1) mm. Its purpose is to ensure proper formation and prevent burns at the top of the seam. The gap b is usually equal to 1.5 - 2 mm, since at the accepted angles of cutting the edges, the presence of a gap is necessary for penetration of the top of the seam, but in some cases, with a particular technology, the gap can be equal to zero or reach 8 - 10 mm or more.

For all types of seams, the complete penetration of the edges of the elements to be joined and the external shape of the seam both on the front side (reinforcement of the seam) and on the back side, i.e. the shape of the reverse roller, are important. In butt and especially one-sided welds, it is difficult to weld the blunting edges to their entire thickness without special techniques that prevent burn-through and ensure good formation of the back bead.

Welds are classified according to a number of criteria. In appearance, the seams are divided into convex, normal, concave (Figure 8). As a rule, all seams are performed with a slight increase (convex). If non-reinforced joints are required, this should be indicated on the drawing. Weakened (concave) fillet welds are performed, which is also noted in the drawing. Such seams are required to improve the performance of welded joints, for example, under variable loads. Butt welds are not weakened, concavity in this case is a marriage. An increase in the size of welds compared to the specified ones leads to an increase in the mass of the welded structure and excessive consumption of electrodes. As a result, the cost of welded structures increases, the labor intensity of welding operations increases.

Figure 8 -

The formation of a smooth transition of the metal of the front and back beads to the base metal is also of great importance, since this ensures high joint strength under dynamic loads. In fillet welds, it can also be difficult to weld the root of the weld through its entire thickness, especially when welding with an inclined electrode. For these welds, a concave cross-sectional shape of the weld with a smooth transition to the base metal is recommended, which reduces the stress concentration at the transition point and increases the strength of the joint under dynamic loads.

By the number of layers and passes, single-layer, multi-layer, single-pass, multi-pass seams are distinguished (Figures 9, 10).

Figure 9 -

Figure 10 - Classification of seams according to the number of layers and passes: I - IV - number of layers; 1 - 8 - number of passes

Weld layer - part of the weld metal, which consists of one or more beads located at the same level of the cross section of the weld. Bead - weld metal deposited or remelted in one pass.

When welding, each layer of a multilayer weld is annealed when the next layer is applied. As a result of such a thermal effect on the weld metal, its structure and mechanical properties are improved. The thickness of each layer in multilayer joints is approximately 5 - 6 mm.

According to the acting force, the seams are divided into longitudinal (flank), transverse (frontal), combined, oblique (Figure 11). The frontal seam is located perpendicular to the force P, the flank seam is parallel, and the oblique seam is at an angle.

Figure 11-

By position in space, lower, horizontal, vertical and ceiling seams are distinguished (Figure 12). They differ from each other in the angles at which the surface of the welded part is located relative to the horizontal. The ceiling seam is the most difficult to perform, the seam is best formed in the lower position. Ceiling, vertical and horizontal seams usually have to be performed during the manufacture and especially during the installation of large-sized structures.

Examples of the designation of welds according to their position in space are given in Figure 13.

Figure 12

Figure 13 -

2. STRUCTURAL ELEMENTS OF WELDED JOINTS DURING MANUAL ARC WELDING

In connection with the importance of the correct preparation of the edges to be welded in terms of quality, economy, strength and performance of the welded joint, state standards have been created for the preparation of edges for welding. The standards regulate the shape and structural elements of cutting and assembling edges for welding and the dimensions of finished welds.

GOST 5264-80 “Seams of welded joints. Manual arc welding. Main types, structural elements and dimensions” and GOST 11534-75 “Manual arc welding. Connections are welded at acute and obtuse angles. Basic types, structural elements and dimensions” regulate the structural elements of edge preparation and the dimensions of the welds made in manual arc welding with a metal electrode in all spatial positions.

It is necessary to note some features of the application of standards. Various methods of electric fusion welding, due to their technological features, make it possible to obtain different maximum penetration depths. By varying the main parameters of the welding mode, constructive types of grooves, it is possible to increase or decrease the penetration depth and other dimensions of the weld.

For this reason, the mentioned standards, which regulate the structural elements of the groove, take into account the possibility of varying the strength of the welding current, voltage, electrode wire diameter (current density) and welding speed. In those cases where the welding process provides the use of high currents, high current density and heat concentration, an increased amount of dullness, smaller groove angles and gap sizes are possible.

In manual arc welding, factors such as the amount of welding current, welding speed and arc voltage change within a small range.

To ensure through penetration of the edges of the product when welding one-sided butt or fillet welds with a sheet thickness of more than 4 mm, welding has to be carried out along pre-cut edges. In manual welding, welders cannot significantly change the depth of penetration of the base metal, but by changing the range of transverse vibrations of the electrode, they can significantly change the width of the weld.

With a sheet thickness of 9 - 100 mm, GOST 5264-80 for butt joints provides for mandatory cutting of edges and a gap, which have a different value depending on the thickness of the metal and the type of joint.

In all cases, using edge preparation standards, one should choose such types of grooves that provide the least volume and cost of edge preparation, volume and mass of deposited metal, full penetration through thickness, smooth shape of the interface of the outer part of the weld and minimum angular deformations.

The quality of welded joints and the efficiency of the welding process are greatly influenced by the cleanliness of the edges and the surface of the base metal adjacent to them, the accuracy of edge preparation and assembly for welding. Blanks for welded parts should be made of pre-straightened and cleaned metal. Cutting out parts and preparing edges is carried out by mechanical processing (on press shears, edge-cutting and milling machines), oxy-fuel and plasma cutting, etc. After using thermal cutting methods, the edges are cleaned from burr, scale, etc. (grinding wheels, metal brushes and etc.).

In some cases, when welding high-alloy steels, the base metal in the heat-affected zone after cutting is also removed mechanically. Before assembling the edge, adjacent areas of the base metal (40 mm from the edge) must be cleaned of oil, rust and other contaminants with metal brushes, shot blasting or chemical pickling. Parts are assembled on tacks (short seams) 20–30 mm long or in special assembly devices.

2.1 Geometric parameters of the weld

Butt seam. The elements of the geometric shape of the butt weld (Figure 14) are the width of the weld - e, the convexity of the weld - q, the depth of penetration - h, the thickness of the weld - c, the gap - b, the thickness of the welded metal - S.

Figure 14 -

Weld width- the distance between the visible lines of fusion on the front side of the weld in fusion welding.

Bulge of the weld

The depth of penetration (penetration) is the greatest depth of melting of the base metal in the weld section. This is the penetration depth of the welded joint elements.

Seam thickness includes weld convexity q and penetration depth (c = q + h).

Gap- distance between the ends of the welded elements. It is set depending on the thickness of the metal to be welded and is 0 - 5 mm (large size for thick metal).

A characteristic of the shape of the weld is the coefficient of the shape of the weld ψsh - a coefficient expressed by the ratio of the width of the butt or fillet weld to its thickness. For a butt weld, the optimal value of ψsh is from 1.2 to 2 (it can vary within 0.8 - 4).

Another characteristic of the shape of the weld is the convexity coefficient of the weld, which is determined by the ratio of the width of the weld to the convexity ψsh of the weld. Coefficient ψsh should not exceed 7 - 10.

The width of the weld and the depth of penetration depend on the method and modes of welding, the thickness of the elements to be welded, and other factors.

fillet weld. The elements of the geometric shape of the fillet weld (Figure 15) are the leg of the weld - k, the convexity of the weld - q, the calculated height of the weld - p, the thickness of the weld - a.

Fillet weld leg- the shortest distance from the surface of one of the parts to be welded to the boundary of the fillet weld on the surface of the second part to be welded.

Figure 15 -

Bulge of the weld is determined by the distance between the plane passing through the visible lines of the boundary of the weld with the base metal, and the surface of the weld, measured at the point of greatest convexity.

Estimated fillet weld height- the length of the perpendicular lowered from the point of maximum penetration at the junction of the paired parts to the hypotenuse of the largest inscribed in the outer part of the fillet weld of a right triangle.

Fillet weld thickness- the greatest distance from the surface of the fillet weld to the point of maximum penetration of the base metal.

If the weld is concave, then measure the concavity of the fillet weld. It is determined by the distance between the plane passing through the visible lines of the fillet weld boundary with the base metal and the weld surface measured at the point of greatest concavity.

Depending on the welding parameters and the form of preparation of the edges to be welded, the shares of the base and deposited metals in the formation of the weld can vary significantly (Figure 16).

The coefficient of the share of the base metal in the weld metal is determined by the formula

K \u003d Fo / (Fo + Fe),

where Fo is the cross-sectional area of ​​the weld, formed due to the melting of the base metal;

Fe - cross-sectional area of ​​the weld, formed due to the deposited electrode metal.

When changing the share of participation of the base and filler metals in the formation of the weld, its composition may change, therefore, its mechanical, corrosion and other properties also change.

Figure 16 -

The main types and structural elements of welded joints for manual arc welding are regulated by GOST 5264-80.

2.2 Weld symbols

Conditional images of seams of welded joints. The main types, structural elements, dimensions and symbols of welded joints and seams in the drawings, as well as the shape and dimensions of the preparation of welded edges from various structural materials used in arc welding, are regulated by standards.

On the drawings of welded products, conditional images and designations of seams are used, given in GOST 2.312-72.

The seam of the welded joint, regardless of the welding method, is conventionally depicted: visible - with a solid main line (Figure 17.a - 17.c), invisible - dashed (Figure 17.d). A visible single weld spot, regardless of the welding method, is conventionally designated with a “+” sign (Figure 17. b).

From the image of a seam or a single point, a leader line is drawn with a one-sided arrow indicating the location of the seam. The leader line is preferably performed from the image of the visible seam.

It is allowed to apply the contours of individual passes to the cross-sectional image of a multi-pass weld, while they must be indicated in capital letters of the Russian alphabet (Figure 18. a).

Figure 18 -

Non-standard seams (Figure 18.b) are depicted with an indication of the structural elements necessary to make a seam according to this drawing.

In the cross-sectional drawings, the boundaries of the seam are applied with solid main lines, and the structural elements of the edges within the boundaries of the seam - with solid thin lines.

2.3 Symbols for welded joints

Auxiliary signs for the designation of welds are given in table 1.

In the symbol of the seam (Figure 19), auxiliary signs are made in solid thin lines. Auxiliary signs must be the same height as the numbers included in the designation of the seam.

The structure of the symbol for a standard seam or a single spot weld is shown in Figure 19. a.

1. The first in the designation are auxiliary signs - “seam along a closed line” and “perform during installation of the product” (table 1).

2. Indicate the number of the standard for the types and structural elements of the seams of welded joints. For example: GOST 5264-80 - Manual arc welding.

3. The alphanumeric designation of the seam is given according to the standard for the types and structural elements of the seams of welded joints. For example, a one-sided butt weld without beveled edges is designated as C2.

Figure 19 -

4. This position indicates the symbol of the welding method according to the standard for the types and structural elements of the seams. The standard allows not to specify the method of welding.

5. The sign and size of the leg for corner, tee joints and overlap, for which the standard provides for the indication of the leg of the seam, for example 5.

6. In this position put down:

For an intermittent seam - the size of the length of the welded area, the sign / or Z and the step size, for example, 50 Z 100;

For a single weld point - the size of the calculated diameter of the point;

For a contact spot welding seam or electric rivet seam - the size of the calculated diameter of the point or electric rivet; sign / or Z and step size, for example 10/80;

For a seam of contact seam welding - the size of the calculated width of the seam;

For an intermittent seam of contact seam welding - the size of the calculated width, the multiplication sign, the size of the length of the welded area, the sign / and the step size, for example 5 x 40/200.

7. In the last place of the designation, auxiliary signs are placed - remove the reinforcement of the seam, etc. (table 1).

If the seam is non-standard, then in its symbol (Figure 19. b) of the above parts, only auxiliary signs (1 and 7) and the part of the designation relating to the structural elements of the intermittent or spot seam (6) are preserved. In the technical requirements of the drawing or the table of seams, the welding method by which a non-standard seam is performed is indicated.

The symbol for the seam is applied:

On the shelf of the leader line drawn from the image of the seam on the front side (Figure 20. a);

Under the shelf of the leader line drawn from the image of the seam on the reverse side (Figure 20. b).

Figure 20 -

For the front side of a one-sided seam, take the one with which welding is performed. For the front side of a double-sided seam with asymmetrically prepared edges, take the one with which the main seam is welded. If the double-sided seam has symmetrical edges, then either side of the seam can be taken as the front.

The designation of the roughness of the machined surface of the seam is applied on the shelf or under the shelf of the leader line after the symbol for the seam (Figure 20.a - 20.b), indicated in the table of seams or given in the technical requirements of the drawing, for example: the roughness parameter of the surfaces of welds Rz 80 µm.

If for the seam of a welded joint a control complex or a category of seam control is established, then their designation may be placed under the leader line (Figure 20). In the technical requirements or the table of seams in the drawing, a link is given to the corresponding regulatory and technical document.

Welding materials are indicated on the drawing in the technical requirements or in the weld table. It is allowed not to specify welding materials.

If there are identical seams in the drawing, the designation is applied to one of the images, and leader lines with shelves are drawn from the images of the remaining identical seams. All identical seams are assigned the same number, which is applied:

On the leader line, which has a shelf with a printed seam designation (Figure 21. a);

On the shelf of the leader line drawn from the image of the seam, which does not have a designation, on the front side (Figure 21. b);

Under the shelf of the leader line drawn from the image of the seam, which does not have a designation, on the reverse side (Figure 21.c).

Figure 21

It is allowed to indicate the number of identical seams on the leader line, which has a shelf with a printed designation (Figure 21. a).

If all the seams in the drawing are the same and are shown on the same side, then the seams are not assigned a serial number and they are marked only with leader lines without shelves (Figure 21.d) except for the seam on which the symbol is applied.

In the drawing of a symmetrical product, if there is an axis of symmetry in the image, it is allowed to mark with leader lines and designate the seams of only one of the symmetrical parts of the product image.

In the drawing of a product in which there are identical components welded with identical seams, it is allowed to mark with leader lines and designate seams only on one of the identical parts shown.

If all the seams in this drawing are made according to the same standard, the standard designation is indicated in the technical requirements of the drawing (by type entry: “Welds according to ...”) or in the table.

It is allowed not to mark the seams in the drawing with leader lines, but to give instructions for welding by writing in the technical requirements of the drawing, if this record unambiguously defines the places of welding, welding methods, types of seams of welded joints and the dimensions of their structural elements in the cross section and the location of the seams.

The same requirements for all seams or a group of seams are given once - in the technical requirements or in the table.

Symbols of standard seams of welded joints

Figure 22 shows the cross-sectional shape of the weld and the symbol for a standard butt weld, respectively. This seam has the following characteristics: a butt joint with a V-shaped bevel of one edge, double-sided, performed by manual arc welding during the installation of the product; reinforcement removed on both sides; weld surface roughness parameter: on the front side Rz 20 µm;

Drawings depicting welded products, welded assemblies, etc., which contain the necessary data for assembly, welding and control, are called assembly drawings. Assembly drawings make it possible to determine how the product is designed and works, what parts it includes, what types of welded joints should be, what welding method should be used to connect parts to each other, what control method should be used to subject welded joints and seams, what technical requirements should match welds, etc.

Figure 22 -

Getting started, the welder must first of all study the drawing: all inscriptions, depicted views, symbols, material of parts, technical requirements for welds.

Terms and definitions for welded structures, assemblies, joints and seams are established by GOST 2601-84.

A welded joint is a permanent connection of two or more elements (parts) made by welding. A welded joint includes a weld, an adjacent area of ​​the base metal with structural and other changes as a result of the thermal action of welding (the heat-affected zone) and areas of the base metal adjacent to it.

A weld is a section of a welded joint formed as a result of crystallization of molten metal or as a result of plastic deformation during pressure welding or a combination of crystallization and deformation.

A welded assembly is a part of a welded structure in which elements adjacent to each other are welded.

A welded structure is a metal structure made from individual parts or assemblies by welding.

The metal of the parts to be joined by welding is called the base metal.

The metal supplied to the arc zone in addition to the molten base metal is called filler metal.

The remelted filler metal introduced into the weld pool or welded onto the base metal is called weld metal.

The alloy formed by the remelted base or base and deposited metals is called the weld metal.

The performance of a welded product is determined by the type of welded joint, the shape and dimensions of welded joints and seams, their location relative to the acting forces, the smoothness of the transition from the weld to the base metal, etc.

When choosing the type of welded joint, the operating conditions (static or dynamic loads), the method and conditions for manufacturing the welded structure (manual welding, automatic welding in factory or installation conditions), savings in the base metal, electrodes, etc. are taken into account.

Types of welded joints. According to the form of conjugation of the parts (elements) to be joined, the following types of welded joints are distinguished: butt, corner, tee, lap (Figure 1).

Welds are subdivided according to the cross-sectional shape into butt (Figure 2, a) and fillet (Figure 2, b). A variation of these types are cork seams (Figure 2, c) and slotted seams (Figure 2, d), performed in overlap joints. According to the shape in the longitudinal direction, continuous and intermittent seams are distinguished.

Butt joints are mainly formed with the help of butt welds (Figure 1, a), with the help of fillet welds - tee, cross, corner and lap joints (Figure 1, b-d), with the help of cork and slotted joints, lap and sometimes tee connections.

Butt welds, as a rule, are continuous; a distinctive feature for them is usually the shape of the cutting edges of the parts to be joined in cross section. On this basis, the following main types of butt welds are distinguished: with edge flanging (Figure 3, a); without cutting edges - one-sided and two-sided (Figure 3, b); with cutting one edge - one-sided, two-sided; with a rectilinear or curvilinear form of cutting (Figure 3, c); with one-sided cutting of two edges; with V-shaped cutting (Figure 3, d); with bilateral cutting of two edges; X-shaped cutting (Figure 3, e). The groove can be formed by straight lines (beveled edges) or have a curvilinear shape (U-shaped groove, Figure 3, e).

a) butt; b, c) tee; d) angular; e) lap

Picture 1 - The main types of welded joints

a) butt; b) corner; c) cork; d) slotted

Picture 2 - The main types of welds

The butt joint is most common in welded structures, since it has a number of advantages over other types of joints. It is used in a wide range of thicknesses of welded parts from tenths of a millimeter to hundreds of millimeters in almost all welding methods. With a butt joint, less filler material is consumed for the formation of a seam, it is easy and convenient to control the quality.

a) with flanging edges; b) without cutting edges;

c, d, e, f) with grooved edges

Picture 3 - Preparation of the edges of the butt welds

Fillet welds are distinguished by the shape of the preparation of the edges to be welded in cross section and the continuity of the weld along the length.

According to the cross-sectional shape, fillet welds can be without cutting edges (Figure 4, a), with one-sided cutting of edges (Figure 4, b), with two-sided cutting of edges (Figure 4, c). In terms of length, fillet welds can be continuous (Figure 5, a) and intermittent (Figure 5, b), with a staggered (Figure 5, c) and chain (Figure 5, d) arrangement of weld segments. T-joints, lap joints and corner joints can be made with segments of seams of small length - spot seams (Figure 5, e).

Cork seams in terms of their shape in plan (top view) usually have a round shape and are obtained as a result of complete penetration of the upper and partial penetration of the lower sheets (Figure 6, a) - they are often called electric rivets, or by melting the top sheet through the previously made in the top sheet hole (Figure 6, b).

a) without cutting edges; b, c) with cutting edge

Figure 4 - Preparation of the edges of fillet welds tee

connections

Figure 5 - Fillet welds of tee joints

Figure 6 - Cross-sectional shape of cork and

welt seams

Slotted seams, usually of an elongated shape, are obtained by welding the upper (covering) sheet to the lower fillet weld along the perimeter of the slot (Figure 6, c). In some cases, the slot can be filled completely.

The form of cutting edges and their assembly for welding is characterized by four main structural elements (Figure 7): gap b, blunt c, bevel angle and bevel angle , equal to or 2 .

Existing methods of arc welding without cutting edges allow welding metal of limited thickness (with one-sided manual welding - up to 4 mm, mechanized submerged arc welding - up to 18 mm). Therefore, when welding thick metal, it is necessary to cut the edges. The bevel angle of the edge provides a certain value of the angle of cutting the edges, which is necessary for the access of the arc deep into the joint and complete penetration of the edges for their entire thickness.

The standard angle of cutting edges, depending on the method of welding and the type of connection, varies from 60 ± 5 to 20 ± 5 degrees. The type of groove and the value of the groove angle determine the amount of additional metal required to fill the groove, and hence the welding productivity. So, for example, the X-shaped groove in comparison with the V-shaped one allows to reduce the volume of deposited metal by 1.6-1.7 times. Reduced edge processing time. True, in this case, it becomes necessary to weld on one side of the seam in an uncomfortable overhead position or turn over the products to be welded.

Dullness c is usually 2 ± 1 mm. Its purpose is to ensure proper formation and prevent burns at the top of the seam. The gap b is usually equal to 1.5-2 mm, since at the accepted angles of cutting the edges, the presence of a gap is necessary for penetration of the weld top, but in some cases, with a particular technology, the gap can be equal to zero or reach 8-10 mm or more.

For all types of seams, the complete penetration of the edges of the elements to be joined and the external shape of the seam both on the front side (reinforcement of the seam) and on the back side, i.e. the shape of the reverse roller, are important. In butt welds, especially one-sided welds, it is difficult to weld the blunting edges to their full thickness without special techniques that prevent burn-through and ensure good back bead formation.

Figure 7 - Structural elements of cutting edges and

assemblies for welding

Welds are classified according to a number of criteria. In appearance, the seams are divided into convex, normal, concave (Figure 8). As a rule, everything

seams are performed with a slight increase (convex). If non-reinforced joints are required, this should be indicated on the drawing. Weakened (concave) fillet welds are performed, which is also noted in the drawing. Such seams are required to improve the performance of welded joints, for example, under variable loads. Butt welds are not weakened, concavity in this case is a marriage. An increase in the size of welds compared to the specified ones leads to an increase in the mass of the welded structure and excessive consumption of electrodes. As a result, the cost of welded structures increases, the labor intensity of welding operations increases.

a) convex; b) normal; c) concave

Figure 8 - Classification of seams in appearance

The formation of a smooth transition of the metal of the front and back beads to the base metal is also of great importance, since this ensures high joint strength under dynamic loads. In fillet welds, it can also be difficult to weld the root of the weld through its entire thickness, especially when welding with an inclined electrode. For these welds, a concave cross-sectional shape of the weld with a smooth transition to the base metal is recommended, which reduces the stress concentration at the transition point and increases the strength of the joint under dynamic loads.

By the number of layers and passes, single-layer, multi-layer, single-pass, multi-pass seams are distinguished (Figure 9, 10).

Weld layer - part of the weld metal, which consists of one or more beads located at the same level of the cross section of the weld. Bead - weld metal deposited or remelted in one pass.

Figure 9 - Classification of seams according to performance: a - one-sided; b - bilateral

Figure 10 - Classification of seams according to the number of layers and passes:

I-IV - number of layers; 1~8 - number of passes

When welding, each layer of a multilayer weld is annealed when the next layer is applied. As a result of such a thermal effect on the weld metal, its structure and mechanical properties are improved. The thickness of each layer in multilayer joints is approximately 5-6 mm.

According to the acting force, the seams are divided into longitudinal (flank), transverse (frontal), combined, oblique (Figure 11). The frontal seam is located perpendicular to the force P, the flank seam is parallel, and the oblique seam is at an angle.

By position in space, lower, horizontal, vertical and ceiling seams are distinguished (Figure 12). They differ from each other in the angles at which the surface of the welded part is located relative to the horizontal. The ceiling seam is the most difficult to perform, the seam is best formed in the lower position. Ceiling, vertical and horizontal seams usually have to be performed during the manufacture and, especially, during the installation of large-sized structures.

a) - longitudinal (flank); b) - transverse (frontal);

c) - combined; d) - oblique

Figure 11 - Classification of seams according to the acting force

Figure 12 - Classification of welds according to their position

in space

Examples of the designation of welds according to their position in space are given in Figure 13

H - lower; P - ceiling; Pp - semi-ceiling; G - horizontal;

PV - semi-vertical; B - vertical; L - in the boat;

Pg - semi-horizontal

Figure 13 - Designation of welds by their position